Re: Simple problem: 0.20 V drop
- From: Jim Thompson <To-Email-Use-The-Envelope-Icon@xxxxxxxxxxxxxxx>
- Date: Sun, 21 Jan 2007 11:46:22 -0700
On Thu, 18 Jan 2007 15:28:01 +0100, Colin Howarth <colin@xxxxxxxxxx>
wrote:
Hi all,
This is a well-known problem (for those using old cameras...):
Mercury oxide cells have a pretty flat 1.35 V open circuit voltage.
They have however been banned in many countries. The best replacement
would seem to be silver oxide which has a voltage of 1.55 V.
the current drawn (by the exposure meter) is low.
So, I'd like to drop 0.20 V along the way somewhere.
a) Zener diodes: don't go down to 0.2 V
b) Schottky diodes: supposed to have a forward drop of 0.15 to 0.45 V
at 1 mA (according to wikipedia) but the drop is current dependent and
varies between samples.
c) Germanium diode?
d) voltage divider with a FET follower? a JFET ?
Is there a standard / best way to do this (with few, smd components)?
Thanks,
colin
How about something simple-minded like....
http://analog-innovations.com/SED/VoltageDropper.pdf
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
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